Work machines such as articulated dump trucks and motor graders often work in environments which give rise to poor traction conditions. As a result, articulated trucks and other types of work machines having two, three or any plurality of axles are typically equipped with some type of traction control device for locking up the respective axles of the machine as well as for locking up the drivelines between the tractor and trailer portions. Typical traction control devices include limited slip differentials or various types of lock-up clutches. These devices are used to send power from the transmission output shaft, through the final drive assemblies, to the wheels. The various types of differentials can be locked or unlocked depending upon the particular operating conditions. When one drive wheel has bad traction, that wheel will turn freely. This action causes a loss of power which can be eliminated by at least locking the differential associated with the particular axle involved. When locked, the differential transfers torque to all wheels under all traction conditions. When unlocked, the torque transferred to the wheels by the differential is limited by the wheel which has the least amount of traction. Limited slip differentials are usually automatically controlled while the lock-up clutches are usually controlled by the machine operator. Similarly, the differential lock-up between the front and rear axles are almost always controlled by the operator. The machine operator must choose both the time and the particular operating parameters under which to engage the lock-up system.
Depending upon the particular type of differentials being used as well as the lock-up system employed, lock-up of the axles cannot always be engaged or disengaged while the machine is moving (on the fly). On those systems where lock-up can be engaged on the fly, the operator has to be constantly aware of certain operating parameters such as the ground speed of the machine as most differential lock-up control systems are limited to engagement below certain speeds. If such systems are engaged above the limiting speed restriction applicable for the particular system being utilized, damage to the system will typically occur as thrust washers and other differential/lock-up components will either wear excessively or suffer immediate fatigue damage and/or failure. This is an undesirable condition.
Another problem associated with manually controlled differential lock systems is that often times, when the front axle differential lock is engaged, steering of the work machine may become difficult or hard depending upon the particular operating conditions encountered. This is particularly true when the front axle differential lock is engaged and the work machine is operating on hard ground. To overcome this situation, the operator must typically manually disengage the entire differential lock-up system. This is likewise an undesirable condition.
In addition, because the drive wheels associated with these types of work machines are differentially geared, when one wheel loses traction, its wheel speed increases and the differential system may experience an overspeed condition. This again is an undesirable condition.
It is therefore desirable to provide a differential lock control system which will automatically monitor both the work machine's ground speed as well as steering pressure and, based upon such inputted parameters, will controllably respond and either engage or disengage the differential lock system based upon such operating parameter.
Accordingly, the present invention is directed to overcoming one or more of the problems as set forth above.